A ground invasion of Iran is now on the table after five months of bombing failed to reopen the Strait of Hormuz — bad news for oil markets, US troops, and Gulf states.

• The strait is still effectively closed, with attacks on ships happening almost daily, so air strikes and a naval blockade clearly are not working.
• The cheap option — arming Kurdish fighters to march on Tehran under US and Israeli air cover — was tried in March and fell apart within days after leaks and Turkish threats.
• The middle option is seizing Iran's Gulf islands, including the one that handles most of Iran's oil exports, but troops there would sit within easy drone and missile range of the coast.
• The real fix is a coastal ground invasion needing tens or hundreds of thousands of troops, and Iran's regular army of some 400,000 has not even fought yet.
• Iran is threatening to hit Kuwait and Bahrain if US troops land, and has already struck a Kuwaiti plant that makes drinking water from seawater.

Outlook: Trump faces a choice between backing down and letting Iran charge tolls in Hormuz or starting a long occupation he has little political support to sustain.